1. Field of the Invention
The present invention generally relates to a liquid crystal display (LCD), and more particularly to a multi-domain vertically aligned (MVA) LCD having specific protrusion pattern for use in a one drop fill (ODF) process.
2. Description of the Related Art
Liquid crystal display mainly comprises two oppositely positioned first and second substrates and a liquid crystal layer interposed therebetween. U.S. Pat. No. 5,263,888 discloses a one drop fill (ODF) process comprising the steps of applying an adhesive onto the entire periphery of the first substrate, dropping the liquid crystal material to the first substrate, superposing the second substrate upon the first substrate and pressing the substrates until a gap between the substrates reaches a predetermined value (typically 3-10 micrometers), and curing the adhesive. In the step of pressing the substrates, the liquid crystal material spreads to fill the space between the substrates thereby forming the liquid crystal layer.
Vertically-aligned (VA) LCD is a mode using a negative liquid crystal material and vertical alignment films. Comparing with the twisted nematic (TN) LCD, the vertically-aligned (VA) LCD provides higher contrast, higher response speed, and excellent viewing angle characteristics for white display and black display. However, the VA LCD still has a critical drawback of a narrow viewing angle. This poses a problem that the application of the VA LCD is limited.
European Patent Publication Number 0884626-A2 discloses a multi-domain vertically aligned (MVA) LCD having domain regulating means for improving viewing angle performance thereof. Typically, the domain regulating means is realized by providing slits on the pixel electrodes of the TFT substrate and providing protrusions on the common electrode of the CF (color filter) substrate. The pattern of the protrusions is continuous and the protrusions are arranged in substantially the same way in all pixels. The protrusions typically have a height of around 1-2μ. For an MVA LCD with a smaller cell gap (3-3.9 μm) design, the spacing between the protrusions and the TFT substrate is about 2-2.9 μm. If the MVA LCD is manufactured by the aformentioned ODF process, bubble is prone to be entrapped between the protrusions in a continuous pattern. In such a case, it may be found that an insufficient degree of spreading of the liquid crystal material will occur during the step of pressing the substrates thereby creating bubbles between the protrusions.